On 9/24/2012 12:25 PM, Dan Edward Dba East edwards wrote:
my suburban lot is small, and i would prefer to make the measurements on my
property; the lot is 120'
N7CL suggested 5 wavelengths as being a viable distance for meaningful
measurements -- that's half a mile. Rudy's 160M measurements were done
at only 700 ft, with a quarter-wave radiator and quarter-wave radials.
That distance seems close, and there are elements of the results from
that series that don't agree with N7CL's observations of the difference
between comparable systems.
One major problem with measurements of this sort is that the presence of
one radial or counterpoise system, even if it isn't hooked up, can
contribute to inaccuracies when measuring the other one. Rudy noted that
when he was doing an extensive series of measurements of 4, 8, 16, 32,
and 64 radials, he added them a group at a time, measured them, then
repeated in reverse order, rolling up those that he was disconnecting to
avoid that problem.
Based on my studies, I'd expect to see differences between various not
bad but non-ideal ground systems of the sort we're discussing here on
the order of a few dB. When you're trying to quantify such small
differences, it doesn't take much to contribute significant errors.
73, Jim K9YC
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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